This invention relates generally to improvements in the means for monitoring and maintaining a vacuum, or partial vacuum, within relatively large containers, and more particularly to an inexpensive means for permanently maintaining and monitoring evacuated, flat-plate solar collector units.
Until now, there has been no specific need or demand for the use of large, permanently evacuated containers, except within specialized industries and for military and research use. The existing applications generally require accurate pressure measurement devices and precise valving and control systems, and they can justify the large cost involved in the use of standard pressure gauges, valves and monitoring systems now available for the purpose. However, the high cost of such gauges and valve systems precludes their use in any application that requires a simple, non-critical means for permanently maintaining and monitoring a vacuum, as in evacuated solar collector systems. In an evacuated solar collector system, for instance, a loss of vacuum and complete failure of the pumping system would merely reduce the operating efficiency of the collectors, but not prevent their continued operation. A further disadvantage of the standard gauges and valving systems presently available is that they require technical knowledge and skill for proper installation and servicing, making the impractical for applications where laymen might undertake such work, as in an evacuated solar collector system.